The lease was signed when "a potential exit of the UK from the Union was not foreseeable", the report said.

"However, the costs associated with the relocation would reasonably be expected to be considered in the negotiations on the withdrawal agreement between the Union and the UK government," it said.

A spokesperson for the UK's department for exiting the European Union said the department has no statement on the issue itself, but pointed to a statement by chancellor Philip Hammond in the UK parliament on 18 April.

"The location of the European Union’s agencies is clearly a matter for the European Union. We cannot credibly seek to leave the European Union and at the same time dictate to it where it should locate its agencies," Hammond said.